The third generation (3G) radio access technologies all use code division multiple access (CDMA) radio modulation technologies, including CDMA 2000, wideband code division multiple access (WCDMA), time division-synchronous code division multiple access (TD-SCDMA), and the like. Neighboring cells or sectors may be distinguished by different orthogonal codes, and a frequency reuse factor of 1 may be achieved (neighboring cells may use a same frequency without causing interference to each other).
The fourth generation (4G) radio access technologies use orthogonal frequency division multiplexing (OFDM) radio modulation technologies, including long term evolution (LTE), worldwide interoperability for microwave access (WiMAX), and the like. If neighboring cells or sectors are on a same frequency, the neighboring cells or sectors may interfere with each other, and consequently networking similar to the second generation (2G) radio access technologies is necessitated in which a frequency reuse factor is 3-7 (cells or sectors using a same frequency are spaced apart by 3-7 cells or sectors).
Bandwidth of a frequency channel is wide (typically 10M or 20M) in 4G, and if the foregoing deployment mode is used, an operator needs to be licensed with extremely wide of frequencies, often at unacceptably high cost and with great technical difficulties. For this reason, a 4G system typically still uses a frequency reuse factor of 1, and employs inter-cell coordination technologies, such as single frequency network (SFN) and coordinated multi-point (CoMP), to suppress interference and increase capacity.
In addition, to increase bandwidth of a single cell, a carrier aggregation (CA) standard is developed for LTE, where multiple frequency channels are combined into one cell.
In the existing architecture, coordination services such as SFN, CoMP, and CA are confined to cells within a single base station, and do not support inter-base station coordination.